1. Field of the Invention
The present invention relates to pre-engineered building construction, and more particularly but not by way of limitation, to improvements in standing seam panel clips for the metal roof industry.
2. Discussion
Standing seam roofs have become the most popular metal roofing assembly due mainly to the avoidance of panel penetration when securing roofing panels to underlying building support structures. Also, since the outer surfaces of a metal roofing assembly are directly exposed to a wide variety of weather conditions, standing seam roofs utilize connectors that provide for expansion and contraction of metal roof panels.
To eliminate or minimize the use of “through fasteners” (fasteners that penetrate the panels to attach them to supporting structure), standing seam metal roofs are secured to the support structure by non-penetrating clip connectors, and the sidelap joints of the standing seam metal roof panels and attaching fasteners are joined together, usually by a seaming process.
The type of seaming utilized will vary depending on the panel design. In some cases, such as in the case of simple interlocking panel arrangements, seam joinder is accomplished by snapping the panels together. In more complex designs, the seaming process will involve pressing the panel sidelaps together to initially interlock the sidelaps as the panels are positioned on the building roof support structures (typically purlins), following which seaming of the joint is achieved by either: (1) a seaming implement or machine that elastically joins the sidelaps; or (2) by a seaming implement or machine that inelastically forming (i.e., by bending and folding) the sidelaps into the standing seam assembly.
Non-penetrating clips that connect roof panels to underlying building support structure (such as purlins) are connected between overlapping panel sidelaps prior to joining and seaming. Panel clip connectors attach the roof to the building structure in the installed position, stabilizing and bracing the roof from environmental factors, such as the uplift forces of a strong wind. The clips also stabilize and brace the support structure, and provide for expansion and contraction of the roof panels as temperature gradients are imposed on the roof members and the underlying building structurals.
To secure roof panels to the underlying support structure, clips typically have tabs designed to be disposed within the panel seam. Such clip tabs are generally shaped as required by the particular shape of the panel design. Because most panels have unique shapes, each clip model is configured for a particular panel shape to which it is to be connected. One important requirement for such clip tabs is that a watertight seal be maintained about the clip tabs in the finally formed standing seam assembly.
Water tightness is usually achieved by a factory applied bead of sealant disposed on the under side of the female sidelap. As adjacent panel sidelaps are seamed, the sealant material is pressed against the top side of the male sidelap to form a watertight dam, preventing water and air from moving between the two sidelaps in the final seam assembly. At the locations where clip tabs are interposed between the male and female sidelaps, such clip tabs prevent the sealant on the female sidelap from contacting the male sidelap, with the female sidelap carried sealant instead being pressed against the tops of the clip tabs at those locations.
That is, as the sealant is compressed to flow toward the male at the clip locations, the sealant must flow around the clip tabs. While encapsulation of the clip tabs is desired, what happens in practice is that the sealant flow at the clip tabs results in gaps in the sealant between the under side of the clip tab and the top of the male side seam. It has been well verified that, because of these gaps, voids and sealant discontinuities, water and air can migrate between the under side of the panel clip tabs and the top side of the male sidelap. In time, this condition will deteriorate the sealing further (such as water freezing, roof leaks, etc.), leading to building leaks and diminished roof panel life.
Past attempts at preventing this condition have included such measures as a factory applied sealant on the underside of each clip tab that aligns with the sealant on the underside of the female sidelap when the clip tab. This sealant on the clip tab is positioned to generally align with the female sidelap carried sealant when the components of the standing seam assembly are assembled. To assure water tightness, the sealant on the female sidelap and on the clip tab, when joined and seamed, must form a continuous seal; this requires that the sealant on the clip tab extend past the tab edges in order to contact the sealant on the female sidelap during sealing. The purpose is to achieve encapsulation of the clip tab and to assure the integrity of the resultant seal between the male and female sidelaps when the seam is formed. However, tests have shown that this approach is less than totally successful, as for many reasons, the continuity of the sealant is far from perfect, there continuing to be some discontinuities in the sealant along the length of the standing seam assembly near the locations of the clips.
Furthermore, although an improvement in providing a continuing watertight seal, the placement of a sealant on the clip tab is costly in material and labor because a separate manufacturing step is required after the final clip forming operation. This means that a separate line must be provided, and that additional handling of the clips is required.
Some manufacturers have attempted to eliminate the clip sealant by designing a clip with perforations, or holes, in the clip tab, the purpose being to allow the sealant on the female sidelap to flow through the tab perforations onto the male sidelap during seaming. This has met with only limited success because the sealant flow through such perforations during seaming has not been consistent to a degree necessary to assure watertight integrity of the seal along the total length of the panel seam, as it has been shown that gaps and discontinuities frequently occur between the stream of sealant extruded through the holes and the sealant extruded around the edges of the clips.
There is therefore a need for a clip design that assures complete sealant encapsulation of the clip tabs with the seaming of a standing seam panel assembly. Preferably, as well, such design would make unnecessary having a sealant pre-applied to the clip tabs prior to installation; that is, complete encapsulation of the clip tabs will be achieved by only the sealant carried by at least one of the panel sidelaps during sealing thereof.